The present invention relates to EPDM compositions containing certain carbon blacks which when extruded or shaped have either a high gloss finish or a textured matte finish.
Carbon blacks have been widely utilized as fillers and reinforcing pigments in the compounding and preparation of EPDM compositions. Carbon blacks are generally characterized on the basis of their properties including, but not limited to, their surface areas, surface chemistry, aggregate sizes, and particle sizes. The properties of carbon blacks are analytically determined by tests known to the art, including iodine adsorption number (I2No.) and dibutyl phthalate adsorption (DBP).
Heretofore generally known carbon black containing EPDM compositions yield profiles having a dull and flat surface finish when extruded or shaped. In contrast, a smooth glossy finish has a high degree of reflectance when viewed at any angle, in part due to the smooth nature of the surface. Conversely, a textured matte finish has a low degree of reflectance due in part to the rugged nature of the surface. EPDM compositions with high gloss or textured matte finishes are useful in industrial applications such as automotive weather stripping.
We have discovered EPDM compositions contain certain carbon blacks that yield profiles having either high gloss or textured matte finishes when extruded or shaped. The EPDM compositions comprise ethylene-propylene diene monomer (EPDM) and a specified carbon black, which when incorporated into the EPDM will provide articles having a desired high gloss or textured matte finish.
The amount of carbon black in the EPDM composition is such that the EPDM composition will, when extruded or shaped, yield profiles having a high gloss or textured matte finish. The amounts of carbon black utilized range from 100 to about 300 parts by weight for each 100 parts by weight of EPDM. It is, however, preferred to amounts varying from about 150 to about 250 parts by weight of carbon black per 100 parts by weight of EPDM.
EPDM is well known and is commercially available from a variety of sources. The EPDM compositions of the present invention may be produced by techniques generally known to those of ordinary skill in the art for mixing rubbers or polymers and carbon black. As will be understood by those of ordinary skill in the art the high gloss and textured matte finish EPDM compositions of the present invention are produced after extruding or otherwise shaping the carbon black-EPDM mixture.
The high gloss or textured matte finish EPDM compositions of the present invention are advantageous for use in applications where a high gloss or textured matte finish is desirable. One such application is automotive weatherstipping.
Other advantages of the present invention will become apparent from the following more detailed description of the invention.
The EPDM compositions of the present invention which will yield a high gloss finish comprise EPDM and a carbon black selected from the group consisting of carbon blacks having a CTAB of about 10 m2/g to about 30 m2/g and a ratio of DBP/CTAB greater than about 4, preferably a CTAB of about 25 m2/g and a ratio of DBP/CTAB of about 5.3; and carbon blacks having a CTAB of about 30 m2/g to about 70 m2/g and DBP greater than about 125 cc/100g, preferably a DBP of about 125 cc/100g to about 160 cc/100g, and most preferably a CTAB of about 47 m2/g and DBP of about 126 cc/100g.
The EPDM compositions of the present invention which will yield a textured matte finish comprise EPDM and a carbon black having a CTAB of about 10 m2/g to about 70 m2/g and a ratio of DBP/CTAB less than about 1.5, preferably a CTAB of about 45 m2/g and a ratio of DBP/CTAB of about 1.0, and most preferably a CTAB of about 67 m2/g and a ratio of DBP/CTAB of about 0.7.
The amount of carbon black in the compositions of the present invention is sufficient to allow the EPDM composition to yield a profile having either a gloss or a textured matte finish after extruding or shaping. The amounts of carbon black to be incorporated into the EPDM compositions of the present invention range from 100 to about 300 parts by weight carbon black per 100 parts by weight EPDM, preferably from about 150 to about 250 parts by weight carbon black per 100 parts by weight EPDM.
The high gloss or textured matte finish EPDM compositions of the present invention may also contain conventional additives such as oils, stabilizers, oxides, acids, curing agents etc. known to those of ordinary skill in the art as useful for incorporation into, and during the formation of, EPDM compositions.
The high gloss or textured matte finish EPDM compositions of the present invention may be produced in any manner known to those of ordinary skill in the art for producing EPDM compositions incorporating carbon blacks. One method for producing the high gloss or textured matte finish compositions of the present invention, utilizing a Banbury BR mixer, is a follows.
The Banbury BR mixer is started and maintained at a temperature of 45xc2x0 C. and a rotor speed of 77 RPM. EPDM is added to the mixer and mixed for approximately 30 seconds. Oil, and preferably zinc oxide and stearic acid, or compounds having similar properties, are added to the EPDM and mixed for approximately 2 additional minutes. The carbon black is added to the mixture and the temperature of the mixing chamber is cooled and maintained at a temperature of below approximately 135xc2x0 C. The carbon black=xe2x80x94EPDM mixture is mixed for approximately 4 xc2xdminutes and then curing agents are added to the mixture. The resulting mixture is mixed for approximately 1 xc2xdminutes while the temperature is maintained at below approximately 135xc2x0 C. The compound is then discharged from the mixer and extruded, or otherwise formed and cooled to form the high gloss or textured matte finish EPDM compositions of the present invention. By way of example, the batch compound may be extruded on a Brabender extruder at 50 RPM and 100xc2x0 C. through a die having an opening of 1 inch in width and 0.020 inch in height. This will yield a profile having a high gloss or textured matte finish.
Although one method for producing the high gloss or textured matte finish EPDM compositions of the present invention has been described, the high gloss or textured matte finish EPDM compositions of the present invention may be produced by other methods for producing polymer or rubber compositions known to those of ordinary skill in the art.
The following testing procedures are used in the determination and evaluation of the analytical properties of the carbon blacks utilized in the following examples.
The DBP (dibutyl phthalate adsorption value) of the carbon black was determined according to the procedure set forth in ASTM D2414. The I2No. (iodine adsorption number) of the carbon blacks was determined according to ASTM D1510. CTAB (cetyl-trimethyl ammonium bromide) absorption value of the carbon blacks was determined according to ASTM Test Procedure D3765-85. Tinting strength (Tint) of the carbon blacks was determined according to ASTM Test Procedure D3265-85a. The CDBP (dibutyl phthalate adsorption value of the crushed carbon blacks) was determined according to the procedure set forth in ASTM D3493-86.
The effectiveness and advantages of the present invention will be further illustrated by the following example.